Unit 3 Flashcards
Cardiac Cycle
all cardiac events that occur during one heartbeat
Contraction of atria or ventricles
Systole
Relaxation of atria or ventricles
Diastole
Why can cardiac muscle initiate its own rhythmic contractions without nervous stimulation?
“Leaky” cell membranes allow influx of Na+ and Ca2+ ions which slowly depolarize the cells to threshold, firing an action potential.
“Pacemaker” cells in the sinoatrial node depolarize fastest and control the rate of contraction of all other cardiac cells
The action potential moves relatively slowly through the atrioventricular node to ensure that atria contract first, and ventricles fill with blood before they contract
factors that affect cardiac contraction strength
inotropes
factors that affect heart rate
chronotropes
epinephrine (effect on heart)
increases heart rate
acetylcholine (effect on heart)
decreases heartrate (muscarinic receptors)
Atropine (effect on heart)
increases heartrate by cholinergic antagonistic action
calcium (effect on heart)
increases force of contractions
Potassium (effect on heart)
regulates heart rhythm
digitalis (effect on heart)
positive inotrope (increases contraction strength)
blood flow in the center of a vessel, not in contact with the endothelium
laminar flow
What components in blood affect viscosity?
How does blood vessel length affect blood flow?
longer vessels = slower flow rate because of drag on greater surface area of endothelium
What is wave summation?
when muscle is stimulated frequently enough that twitches overlap
What is the absolute refractory period?
the period during which APs can’t be generated no matter how strong the stimulus
How long is the total refractory period of cardiac muscle?
200-250 ms
What is an extrasystole?
an extra contraction
When is it possible to stimulate an extrasystole?
What is vagal escape?
sympathetic stimulation of the heart to increase rate and blood pressure in response to a muscarinic stimulation causing reduction of blood pressure
What causes vagal escape?
sympathetic reflexes
how many APs does the SA node generate per minute without external stimulation?
100
Which organelle in a cardiac muscle cell stores calcium?
sarcoplasmic reticulum
What are the different layers of “bundling” within a skeletal muscle?
A muscle is covered by epimysium and is a bundle of…
Fascicles which are covered by perimysium and are bundles of…
**Muscle fibers (muscle cells) **which covered by endomysium and are bundles of…
Myofibrils which are bundles of…
Actin and myosin proteins
What is the cell membrane of a muscle cell?
sarcolemma
What are the 3 types of muscle and their general functions and structure?
Skeletal - position and move skeleton, large, multinucleate, striated cells
Cardiac - pump blood (heart), short, branched, striated uninucleate cells connected by intercalated disks
Smooth - movement of material into, out of and within body, small, uninucleate, unstriated cells
What is the cytoplasm of a muscle cell?
What is the name and function of the structure that wraps around each myofibril like a piece of lace?
And its parts?
Sarcoplasmic Reticulum
Describe the T-tubules. What are they, what do they do and what is the structure they make up with the terminal cisternae?
What neurotransmitter is used at neuromuscular junctions?
Acetylcholine
What are 4 characteristics/abilities of muscle tissue?
- Can shorten (contraction)
- Can stretch/lengthen (relaxation)
- Elasticity (returns to normal)
- Excitability (can create APs or be stimulated by nerve)
What is a motor unit?
A unit in the somatic NS and musculoskeletal system consisting of a motor nerve and all the muscle cells it innervates
How many motor units per muscle?
How does this ratio affect control?
- Varies greatly, but most muscles have > 1 motor unit
- nerve to muscle cell ratios can be anything… 1:13, 1:137, 1:529, etc.
- the fewer muscle cells per nerve, the greater the degree of fine control over that muscle
Describe the transfer of a signal between motor neuron and muscle cell at the motor end plate.
- AP travels to axon terminal of motor nerve
- Voltage-gated Ca channels open at synaptic knob, Ca diffuses in, attaches to synaptic vesicles
- Synaptic vesicles full of acetylcholine exocytosize to synaptic cleft and attach to chemically-gated Na channels
- Na diffuses in to create AP on muscle cell which travels deep into cell
What are the bundles of proteins within a single muscle cell called?
What 2 major proteins make them up?
And what is a single functional unit within this bundle called?
- Myofibrils
- Actin and Myosin
- Sarcomere
How are myofilaments laid out within a relaxed myofibril?
Describe it and draw it.
- Alternating bands of thicker myosin and thinner actin myofilaments line the cell (w/ Z-discs intersecting actin and M lines intersecting myosin)
How is acetylcholine removed from the chemically-gated Na channels?
1) enzymatic breakdown via **acetylcholinesterase **into acetyl and choline
2) re-uptake into the pre-synaptic axon terminal
How does innervation of skeletal and cardiac muscle differ?
- Each skeletal muscle cell is innervated by communication with a synapse
- Many cardiac muscle cells are innervated by one synapse and communication via intercalated disks (gap junctions) between cells
How does an AP affect myofibrils of a muscle cell nearly simultaneously?
T-tubules extending deep into cell allow fast (extracellular, non-cytosolic) travel of ions to the deeper myofibrils
Describe the transmission of action potentials deep into muscle cells via T-tubules and the release of calcium from terminal cisternae of the sarcoplasmic reticulum.
Draw it.
1) APs begun by ACh at motor end plate travel along sarcolemma into T-tubules
2) APs cause voltage change at triad, opening Ca channels on terminal cisternae for diffusion of Ca into sarcoplasm
What are some functions of muscle?
1) produce movement
2) open and close passageways
3) maintain posture and stabilize joints
4) generate heat
What is the theory behind muscle contraction called?
Describe it.
Sliding Filament Theory
or Contraction Coupling Process
**- **Myosin pulls actin (z-lines) closer together
What is the functional unit of a muscle?
What is it made up of?
Sarcomere
- Actin and myosin filaments
- Z-lines bisect actin filaments
- M-lines bisect myosin filaments
- A-bands are areas where myosin is
- I-bands are where it is not
- H-zone is portion of A-band w/out actin
Describe the structure of actin and its accessory proteins.
Draw it.
2 strands of globular actin
2 strands of tropomyosin
Troponin complexes
How does myosin bind to actin? Describe the process.
Draw it.
1) Ca ions bind to troponin complexes
2) Tropomyosin then moves away from myosin binding sites on actin
3) Myosin heads w/ actin binding sites move in and bind
How is a myosin filament structured?
Describe and draw it.
Myosin filaments are made of many myosin molecules.
There is a “tail” of two strands twisted together and “heads” like two golf club heads at the end of the tail (AKA cross-bridge heads).
Describe the contraction cycle.
Draw it.
1) Myosin heads bent w/ ATP attached, unbound to actin
2) Myosin hydrolyzes ATP, energy “cocks” head, myosin binds weakly to actin
3) “Power Stroke” - Ca signal moves tropo/tropo complex, P leaves myosin, heads re-bend pulling actin toward M-line, ADP leaves myosin
4) Myosin is bound to actin, ATP re-binds myosin, cycle repeats.
What are some sources of ATP within the muscle?
1) stored ATP (lasts 6 seconds)
2) creatine phosphate (donates phosphate to ADP to make ATP, lasts 10 seconds)
3) cellular respiration ( 2 ATP glyc, 2 ATP krebs, 26 ATP ETC)
What is the force of contracting muscle and its opposing force called?
Contraction - muscle tension
Opposing force - load
What is a single contraction-relaxation cycle in skeletal muscle called?
What are its parts?
Twitch
Latent Period - between muscle AP production and tension development
Contraction Phase
Relaxation Phase
How can nervous signals cause contraction force increase?
- by increasing frequency of APs stimulating muscle fiber to cause summation
- increased AP frequency does not allow full relaxation between stimuli
What is the state of continuous maximal contraction called?
And its two kinds?
Tetanus
incomplete or unfused tetanus - slight relaxation between stimuli
complete or fused tetanus - no relaxation
How are graded muscle contractions of different strengths and durations created?
Recruitment of different types and numbers of motor units.
Low threshold neurons control fatigue-resistant slow-twitch minimal force fibers.
Medium threshold neurons stimulate fatigue-resistant fast-twitch oxidative-glycolytic fibers
High threshold neurons stimulate glycolytic fast-twitch fibers
What kind of contraction creates force and moves a load?
Isotonic Contraction
What kind of contraction creates force but does not move a load?
isometric contractions
Describe the flow of blood from its entrance into the heart to its exit from the heart.
- Superior and Inferior Vena Cava
- Right Atrium
- Tricuspid Valve
- Right Ventricle
- Pulmonary Semilunar Valve
- Pulmonary Trunk & Arteries
- Lungs (pulmonary capillaries)
- Pulmonary Veins
- Left Atrium
- Biscuspid (Mitral) Valve
- Left Ventricle
- Aortic Semilunar Valve
- Aorta
What is the primary function of the cardiovascular system?
Transporting materials to and from all parts of the body.
1) Nutrients, water, gases from outside
2) materials between cells
3) wastes from cells
What are the 3 components of the cardiovascular system?
Heart
Blood Vessels
Blood
What are the two circuites of the cardiovascular system?
Systemic
Pulmonary
What are the serous membranes around the heart?
Visceral pericardium - directly on heart
Parietal pericardium - lines pericardial cavity
What does an electrocardiogram look like?
Draw it.
What does each part of the PQRST of an EKG represent?
P Wave - atrial depolarization (from SA node)
QRS Wave - ventricle depolarization (and atrial repolarization)
T Wave - ventricle repolarization
What are the structures of the conduction system of the heart?
Draw them.
Sinoatrial (SA) Node - pacemaker (right atrium)
Atrioventricular (AV) Node - delays signal to ventricles by 2 ms so they contract after atria
Bundle of His - send signals from AV node to bundle branches
Left/Right Bundle Branches - run down IV septum to Purkinje fibers
Purkinje Fibers - conduct signals along walls of ventricles
What is a miscommunication in the heart’s electrical system known as?
Where does it usually occur and why?
Fibrillation
Usually in left atrium because of distance from SA node
How do the atrial and ventricular contractions move?
Atrial start superiorly and move inferiorly to move blood down into ventricles
Ventricular are opposite to move blood up and out semilunar valves
Describe an action potential in electrical conduction cells of the heart.
Draw its graph.
- Increased Na permeability causes a constant drift from -60 mv resting state to threshold
- -40 mv threshold is reached, voltage-gated Ca channels open
- +20-30 mv max voltage is reached via Ca influx
- K efflux repolarizes to resting, no hyperpolarization
Describe an action potential being created in a myocardial contractile cell.
Draw its graph.
- -90 mv resting state rises to -60 mv threshold due to Na influx
- voltage-gated fast Na and slow Ca channels open to depolarize cell to +30 mv
- fast Na channels close, slow Ca channels stay open, causing Ca plateau, lengthens abs. refractory period and allows for simultaneous contraction of multiple cells
- K+ efflux repolarizes
What part of the cardiovascular system’s pressure is being measured when blood pressure is measured?
During what activity?
arterial pressure during ventricular activity
systole - contraction
diastole - relaxation
What is pulse pressure?
Its ideal value?
Systolic minus diastolic
30-40 mm Hg
What is cardiac output?
the amount of blood pumped out of the heart each minute
How is cardiac output calculated?
What is the usual cardiac out put in an adult?
Heart Rate x Stroke Volume
(75 bpm x 70 mL = 5,250 mL)
about 5.2 L/min
What happens to cardiac output if heart rate changes?
Cardiac output stays the same.
An increased HR means a decreased stroke volume, so CO stays same.
Decreased HR = increase SV.
What is the amount of blood pumped out of each ventricle each beat?
Stroke Volume
about 70 mL
What 3 factors affect stroke volume?
- Contractility -
- Preload - degree of stretch (Frank-Starling Law)
- Afterload - diastolic value
What 3 factors affect peripheral resistance?
- diameter - smaller diameter = less laminar flow
- length - greater length = more drag against sides
- viscosity - more viscous = slower flow
What are the 3 layers of a blood vessel?
- Tunica Interna - endothelium
- Tunica Media - smooth muscle
- Tunica Externa - CT
What are the differences between arteries and veins?
Arteries
- away from heart
- small lumen
- higher pressure
- thicker tunica media
- maintain shape
Veins
- towards heart
- large lumen (contain 60% of blood)
- low pressure
- thin tunica media
- shaped by surrounding tissues
- have valves
What are the different types of arteries?
Elastic - aorta, pulmonary, their branches
**Muscular - **AKA medium or distributing, renal, brachial, femoral, etc.
**Arterioles - **just before capillary beds, control BP and capillary flow via vasoconstriction/dilation
What are the different types of veins?
Large Veins - sup. & inf. vena cava (0-5 mm Hg)
Medium Veins - brachial, femoral, renal, etc. (10 mm Hg)
Venules - drain capillary beds (20 mm Hg)
What are the three types of capillaries and where are they found?
- **continuous - **solid endothelium (common)
- fenestrated - holes in endothelium (kidneys)
- sinusoidal - very porous endothelium (spleen, liver, red bone marrow)
What are the two forces that influence movement of substances between capillaries and tissues?
Which forces fluid out of capillaries and which draws fluids back in?
What is each based on and can each change?
Blood Hydrostatic Pressure - normal blood pressure based on pumping of heart, descreases as distance from heart increases, pushes fluids out of capillaries
**Blood Osmotic Pressure - **keeps fluids in, based on non-diffusable solutes, doesn’t change
Draw the capillary with its differing pressures on each end, showing how they influence movement of substances into and out of tissues.
What is the composition of blood?
Components and percentages.
**Plasma (55%) **- water, ions, hormones, gases, wastes
Formed Elements (45%) - RBCs (44%), WBCs and platelets (1%)
What are the 5 functions of blood?
- Transport
- Temperature Control
- Immunity
- pH Control
- Blood Clotting
Describe erythrocytes, their functions and characteristics.
- released mature from bone marrow without nucleus or organelles
**- binconcave **for flexibility and surface area
- live 100-120 days b/c of lack of organelles
- contain hemoglobin to carry oxygen and carbon dioxide
Describe hemoglobin, its structure and function.
- a quaternary protein structure
- consists of four 4 Heme groups and 4 Globin proteins
- carries O2 and CO2 separately
- 200-250 million per RBC, so on RBC can carry both gases
Which gas loads more easily onto hemoglobin?
Describe loading of gases.
CO2loads more easily
first O2 loads easily, second requires pressure, 3rd/4th are easy
Describe RBC movement through capillaries and how it is advantageous to function.
Draw it.
Biconcave RBCs bend into kidney bean-like shape and move slowly through capillaries to allow for gas exchange.
How does the body compensate for elevational changes in oxygen pressure?
It increases erythropoiesis at higher elevations to increase its ability to transport oxygen.
How are erythrocytes broken down and removed from the body?
- primarily in spleen, also in liver if necessary
- reticular fibers of these organs create network for flexible RBCs
- old, inflexible RBCs phagocytized by WBCs
- Hemoglobin is recycled
Describe hemoglobin recycling.
- Broken into Heme and Globin
- Heme is reused or turned into bilirubin by spleen, sent to liver and made into bile salts (either stored in GB or straight to SI)
- Globin is re-used or broken down into amino acids
Name the two subcategories and 5 types of leukocytes.
What are the characteristics of the 2 subcategories?
**Granulocytes (granules, lobed nuclei)- **basophils, neutrophils, eosinophils
**Agranulocytes (no granules, large, unlobed nuclei) - **lymphocytes, monocytes
What is most common leukocyte?
Describe it.
Neutrophil
- lobed nuclei
- phagocytic
- pink granules
What is the 2nd most common granulocyte?
Describe it
Eosinophil
- phagocytic
- involved in parasitic infection and allergy
- red/orange granules
What is the least common leukocyte?
Describe it.
Basophil
**- **involved in allergy
- releases histamine in inflammation and heparin for anti-coagulation
- blue-purple granules
What is the 2nd most common WBC?
Describe it.
Lymphocytes
- large central nuclei almost to plasma membrane
- two kinds, B and T
- specific to certain pathogens, have ‘memory’ for antigens
T Cells (thymus)
- attacks and kills cells
- helper T cells help lymphocyte production
B Cells (bone)
- produce antibodies
- mark pathogens for removal
What is the largest WBC?
Describe it.
Monocyte
- phagocytic
- large, kidney-shaped nucleus
- migrates to tissues to become macrophage
What is hematocrit?
the volume percentage of RBCs in blood
about 45% for men
about 40% for women
How does blood typing work?
Draw out the chart.
A has A-antigen and B-antibody
B has B-antigen and A-antibody
AB has both antigens and neither antibody
O has neither antigen and both antibodies
Describe how Rh factor works.
Rh factor is a surface antigen on RBCs.
Rh+ people have it, Rh- people don’t
Rh+ people can receive either blood type because they do not create antibodies to Rh factor.
Rh- people can only receive Rh- blood because they DO produce antibodies. (They can receive + blood once, but then are sensitized).
What are the names for the surface antigens and their antibodies in ABO typing?
Agglutinogens (antigens)
**Agglutinins **(antibodies)
What are platelets called and where do they come from?
Thrombocytes
**- **from megakaryocytes
What is blood clot formation called? Describe its 3 steps.
Hemostasis
**1. Vascular Spasm **- damaged endothelium releases vasoconstrictors
**2. Platelet Plug - **releases platelet-activating factor (PAF) which attracts platelets
3. Coagulation - fibrin net forms around platelet plug
What is a floating blood clot called?
Thrombus
What is the process of fibrin net breakdown and release of platelets?
Fibrinolysis
What are the two types of coagulation and their characteristics?
Intrinsic
- natural
- internal
- slow
Extrinsic
**- **fast
- usually due to trauma
What is the important protein in coagulation called?
Describe its creation.
Thrombin
- Ca++ acts on Factor X
- Factor X becomes active
- Ca++ acts on Active Factor X
- Active factor X acts on Prothrombin
- Prothrombin converts into thrombin
What molecules does thrombin act on to aid in clotting and clot breakdown?
Clot Formation
- thrombin acts on fibrinogen to form **fibrin **and Factor XIII to form Active Factor XIII
- Fibrin plus Ca++ and active factor XIII forms cross-linked fibrin net around the platelet plug
Clot Breakdown
- thrombin acts on plasminogen to form plasmin
- plasmin performs fibrinolysis on cross-linked fibrin net, breaking it down to release platelets
what are the stem cells that blood cells come from?
hemocytoblasts
hematopoietic stem cells
what is the pH range of blood?
7.35-7.45
